Mathematica: A flexible design environment for neural networks

Several neural networks were developed inMathematica in order to explore the role of “spiky” neurons in neural network memory simulations. UsingMathematica for this task confirmed its value as a powerful tool for neural network development: It exhibited distinct advantages over other environments in programming ease, flexibility of data structures, and the graphical assessment of network performance.     

Need probability affects retention: A direct demonstration

Recent memory theory has emphasized the concept ofneed probability—that is, the probability that a given piece of learned information will be tested at some point in the future. It has been proposed that, in real-world situations, need probability declines over time and that the memory-loss rate is calibrated to match the progressive reduction in need probability (J. R. Anderson & Schooler, 1991). The present experiments were designed to examine the influence of the slope of the need-probability curve on the slope of the retention curve. On each of several trials, subjects memorized a list of digits, then retained the digits in memory for 1, 2, 4, 8, or 16 sec. Some trials ended with a recall test; other trials ended with the message, “no test.” In Experiment 1, the likelihood of encountering a memory test (i.e., the need probability) was made to either increase or decrease as the retention interval increased; in Experiment 2, need probability either was flat (invariant across retention intervals) or decreased as the retention interval increased. The results indicated that the shape of the need-probability curve influenced the slope of the retention curve (Experiment 1) and that the effect became larger as the experimental session progressed (Experiment 2). The findings support the notion that memory adapts to need probabilities and that the rate of forgetting is influenced by the slope of the need-probability curve. In addition, all of the forgetting curves approximated a power function, suggesting that need probability influences the slope but not the form of forgetting.     

REDUCING ESCAPE BEHAVIOR AND INCREASING TASK COMPLETION WITH FUNCTIONAL COMMUNICATION TRAINING,EXTINCTION AND RESPONSE CHAINING

The effects of functional communication training, extinction, and response chaining on 3 subjects' escape-maintained aberrant behavior were evaluated using a multielement design. Functional communication training consisted of teaching subjects a verbal response that was functionally equivalent to their aberrant behavior. Subjects initially were allowed to escape from a task contingent on the trained verbal response. In subsequent treatment phases, escape was contingent on the trained verbal response plus the completion of the specified number of steps in the task (response chaining). The number of steps was increased until a subject completed the task to obtain a break. Results showed that the treatment reduced rates of aberrant behavior and that the chaining procedure was effective in decreasing the availability of escape.     

The recollective experience of cross-modality confusion errors

There are at least two qualitatively different types of subjective experience that can accompany accurate recognition memory. Sometimes recognition is accompanied by conscious recollection of the learning episode (i.e., it isremembered), and in other cases it is not (i.e., it is simplyknown that the item is old). In the present study, we assessed the subjective experience that accompanies crossmodality confusion errors (misidentifying words as pictures) by measuring the extent to which subjects claimed toremember versusknow that the item was presented as a picture. The results of two experiments demonstrate that cross-modality confusion errors are often accompanied by conscious recollection, although not to the same extent as accurate memories. The findings also show that there is considerable overlap in the recollective experience that accompanies accurate and erroneous memories. Finally, the results support the contention that recollective experience cannot be directly inferred from test performance.     

Piaget and Vygotsky Revisited: Dialogue or Assimilation?

In response to suggestions for merging Piagetian and Vygotskian psychology on the basis of their apparent similarity (e.g., Glassman, 1994), it is argued that numerous differences between the two paradigms constitute fundamental principled disagreements, and that these ought not to be minimized or simplified. Some fundamental differences involve underlying philosophy, social influences on development, the nature of the developmental process itself, developmental stages, and universality of cognitive structures. It is argued that a project of combining Piagetian and Vygotskian psychology would be premature at best, and that continued dialogue between these two distinct perspectives would be of greater value.     

Target and nontarget grouping in visual search

Results recently reported by Driver, McLeod, and Dienes (1992) are used to contrast three accounts of visual search—in particular, their mechanism for easy conjunction search. In the Driver et al. study, the target was defined by a conjunction of form and movement; the key manipulation was phase in both target and nontarget motion sets. Mechanisms working separately on each display element (inhibition from nontarget features, facilitation from target features) are unable to explain large effects of phase, since this is defined only by relationships between one element and another. As implemented in the guided search model of Cave and Wolfe (1990), local suppression between similar elements is also unable to account for the results. More promising is an approach based on perceptual grouping: Elements moving in phase can be selected (target motion) or rejected (nontarget motion) as a group. Rather than a bias against elements that are similar to or grouped with their neighbors, there is a bias to treat grouped elements together.     

Self-esteem and Rogers' core conditions in close friends: A latent variable pathanalysis of panel data

A LISREL or path analysis with latent variables was used to test the Rogerian-derived hypothesis that self-esteem is determined by the degree to which a person has a current close friend who is seen to be unconditionally accepting, empathic, and congruent. The revised Barrett-Lennard (1964) Relationship Inventory and Rosenberg (1965) Self-Esteem Scale were completed by 38 female and 28 male students on two occasions 15 weeks apart. The hypothesis was conjimzed for unconditionality of acceptance (which was positive) and the core conditions combined. In addition, the temporal relationships between the core conditions were analysed. Level of acceptance was reciprocally related to both empathy and congruence, while prior congruence had a negative but nonsignajicant association with unconditionality of acceptance.     

Intelligence and the Frontal Lobe: The Organization of Goal-Directed Behavior

Basic to the study of individual differences is the concept of “general intelligence” or Spearman'sg.In this article we suggest thatgis largely a reflection of the control functions of the frontal lobe. A series of experiments investigates a phenomenon we callgoal neglect:disregard of a task requirement even though it has been understood and remembered. Subjectively it is as though the neglected requirement “slips the subject's mind.” Previously described in frontal patients, we show that goal neglect can also be seen in some members of the normal population. In line with conventional distinctions between controlled and automatic processing, eliciting conditions for goal neglect include novelty, weak error feedback, and multiple concurrent task requirements. Under these conditions neglect is linked closely togand extremely common after frontal lesions. Following many other models, we suggest that behavior in any task is structured by a set of action constraints or requirements, derived in part from verbal instructions and specified at multiple levels of abstraction. A frontal process of constraint or requirement activation is fundamental to Spearman'sg.